ChanServ changed the topic of ##yamahasynths to: Channel dedicated to questions and discussion of Yamaha FM Synthesizer internals and corresponding REing. Discussion of synthesis methods similar to the Yamaha line of chips, Sound Blasters + clones, PCM chips like RF5C68, and CD theory of operation are also on-topic. Channel logs: https://freenode.irclog.whitequark.org/~h~yamahasynths
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<whitequark>
KitsuWhooa: that doesn't actually work
<whitequark>
at all
<KitsuWhooa>
the vice thing? Possibly
<whitequark>
no, the rosin thing
<KitsuWhooa>
oh, really?
<whitequark>
yeah
<whitequark>
try it if you want
<KitsuWhooa>
I probably will at some point, yeah
<whitequark>
there's no reason rosin should do anything to epoxy, in principle, and so it doesn't *shrug*
<whitequark>
no idea why people claim it should
* KitsuWhooa
shrugs
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<cr1901_modern>
KitsuWhooa: So Project Tasos is your website?
<KitsuWhooa>
Where did you see "Project Tasos"? :p
<KitsuWhooa>
"website", if you can even call it that
bofh_ is now known as mofh
* cr1901_modern
remembers when SSRG was a thing
<KitsuWhooa>
tasossah.com basically the desktop I'm typing this message on :p
<KitsuWhooa>
heh
<KitsuWhooa>
if I'm not mistaken, voice hosted the IRC server for SSRG at some point
<cr1901_modern>
I have no idea who voice is. I was 12 when SSRG (the Andy Wolan-run one) died lol
<KitsuWhooa>
he's the one behind randomsonicnet, which is why I mentioned him :p
<cr1901_modern>
By the time Sonic Retro rolled around, I lost interest. Seems less true now, but that was a cesspool of elitists
<KitsuWhooa>
I wasn't around for most of it
<KitsuWhooa>
mostly because I was a dumb kid back then :p
<KitsuWhooa>
well, the late years
<KitsuWhooa>
According to the sonic retro wiki, SSRG was created on: Fall 1996. I didn't realise it was that old
<andlabs>
voice vanished around the time I started bieng around
<andlabs>
so eh
<andlabs>
in other news I transcribed the 3-page BASIC program for testing that Sequential MIDI interface
<andlabs>
I just need a pedal and a drum machine timing thingy if I want to test the non-MIDI aspects
<andlabs>
and now I'm just frustrated that there is no clear standard terminology for these things
<andlabs>
is the footswitch thing a quarter-inch jack?
<andlabs>
is there a name for it/
<andlabs>
is there a name for the protocol?
<andlabs>
what about the name of the protocol used for the drum machine timer?
<andlabs>
I'm going to bed good night
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<cr1901_modern>
>6.46GB free
<cr1901_modern>
I suppose I should remove shit so I can attempt to install Ardour...
* ZirconiumX
grumbles about Ardour
<cr1901_modern>
Well, it's "inferior FOSS product that I stand a chance at helping get better", or "superior non-FOSS product that I don't want to pay for and have little chance of actually improving"
<cr1901_modern>
Ardour, like sigrok/pulseview is also sadly difficult to build on Windoze- actually I think it may be even more difficult.
<Sarayan>
what's ardour already?
<ZirconiumX>
I realise this, and I decided to go with the superior non-FOSS option
<cr1901_modern>
Cross platform FOSS-daw
<ZirconiumX>
Digital Audio Workstation; aka music production software
<Sarayan>
oh yeah, I remember it
<Sarayan>
couldn't really make heads or tails of it
<Sarayan>
the blender effect I guess
<cr1901_modern>
Basically I want to connect my mpk mini to it, and have a Yamaha core play music on the other end
<ZirconiumX>
Yeah this is where I'd break out REAPER.
<ZirconiumX>
It disappoints me greatly to say this
<Sarayan>
reaper?
<ZirconiumX>
But the best DAW I've ever used is Logic Pro.
<ZirconiumX>
Sarayan: a different non-FOSS DAW.
<ZirconiumX>
Linux friendly though.
<cr1901_modern>
How do I put this nicely? I don't actually like entering music through a computer. I mainly wanted something that let me screwaround with a keyboard interface while having Yamaha sounds come out the other end.
<cr1901_modern>
A DX7 w/ reprogrammable Yamaha core, if you will
<ZirconiumX>
And that's fair enough.
<cr1901_modern>
Trackers suck for entry, I don't expect to use a DAW beyond for screwing around, I have an old version of Finale I _really_ need to dump, Rosegarden is *nix only, MuseScore isn't great
<cr1901_modern>
Honestly, MML entry is the only thing I've had any amount of success with for writing music, but that doesn't play nice w/ DAWs AFAICT
<ZirconiumX>
At that point though you might as well just use qjackctl or whatever to hook up midi devices
<ZirconiumX>
Assuming you have a midi keyboard anyway.
<cr1901_modern>
Pretty sure jack implies Linux only?
<cr1901_modern>
And correct, only a MIDI keyboard
<cr1901_modern>
I wonder if a passthrough to a Yamaha core VST is possible
<ZirconiumX>
Jack also runs on the BSDs I think, but that's probably not what you're asking :P
<ZirconiumX>
Audio routing in general sucks.
<cr1901_modern>
the other problem is I'll need to have _some_ way to change VST parameters on the fly, to ya know, test patches
<Sarayan>
you know you can connect a midi keyboard to mame
<whitequark>
what yamaha vst are you using?
<Sarayan>
wq, got yesterday's mail?
<whitequark>
Sarayan: yep
<Sarayan>
good
<Sarayan>
so you have the tracking number and everything
<Sarayan>
hapefully this time :-)
<whitequark>
yep
<Sarayan>
I've put 4 cis I had around
<whitequark>
four... what?
<Sarayan>
ICs sorry
<cr1901_modern>
whitequark: None, atm. But there are a few good ones I was looking at in June, incl one based on nukeykt's core.
<cr1901_modern>
Sarayan collects cis ppl... not sure that's a valuable commodity
<Xyz_39808>
MML :o
<cr1901_modern>
Yes Xyz_39808, I hate it and love it for the same reason- terse.
<Sarayan>
the votrax, some yamaha I forget which, a cat702 (security chip) I'm curious what's inside (I otherwise reversed it ages ago) and an original 8008
<whitequark>
ohh neat
<whitequark>
I assume 8008 has long been imaged?
<Sarayan>
I actually don't think so
<Sarayan>
hence why I added it
<Sarayan>
ahhh, it has
<Sarayan>
oh well
<Sarayan>
enjoy it anyway :-)
<whitequark>
want me to do something specific with it?
<cr1901_modern>
Exhibit B: https://github.com/jpcima/ADLplug This is _half_ of the link I was looking for, but my intent was to use a VST built from this
<cr1901_modern>
At least this time now it's archived in the logs lmao
* cr1901_modern
will look for the other link later- it had a bunch of rec's for MAME Yamaha cores converted to VSTs
<ZirconiumX>
I'm presuming you also know of Dexed, cr1901_modern?
<cr1901_modern>
I know the name, but I would need a refresher
<ZirconiumX>
DX7 VST; FOSS
<cr1901_modern>
ahhh yes, that rings a bell
<cr1901_modern>
Almost certainly that VST was linked in the actual website I'm looking for
<cr1901_modern>
(it's easy enough to find, I just don't feel like going through an sqlite db to find the link lmao)
<Sarayan>
ZX: I rememebre plgdavid saying that dexed was wishful thinking at best :-)
<cr1901_modern>
whitequark: Btw, remember how you were discussing a patch editor a few days ago? Well, the images on this repo give what I _think_ is a sleek GUI for making patches: https://github.com/jpcima/ADLplug
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<cr1901_modern>
I do hope plgdavid releases his docs in reasonable time so another project is unnecessary.
<ZirconiumX>
https://www.youtube.com/watch?v=D3xCO8tB1kg <-- the difference is noticeable in that Dexed is brighter than the original hardware, but I don't think that's actually a bad thing
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<ZirconiumX>
Possibly unpopular opinion: flawed emulation can have its advantages in giving said emulator its own distinct quality
<ZirconiumX>
Not to say that emulation *should* be flawed, but that it's not necessarily a bad thing
<cr1901_modern>
I don't have a drama-free response to that
<Sarayan>
You heretic, etc
<ZirconiumX>
That's why it's listed as an unpopular opinion :P
<cr1901_modern>
Well even my drama-filled response doesn't really take a side, other than "I would _personally_ prefer to remove as much decay of state due to the elements of time as possible"
<cr1901_modern>
I had the opportunity to get a DX7 from a friend for a reasonable price in 2013. They even offerred a discount knowing it was "something I wanted but I couldn't really afford". Neither of our fault, but we fell out of contact, and I've no way to contact them now. I _really_ should've bought it.
<cr1901_modern>
WHY didn't I do it?! Was 2612 the only chip that mattered to me back then? :/
<ZirconiumX>
Hang on, I'll go buy a DeLorean
<ZirconiumX>
:P
<cr1901_modern>
By the time you get one of those, I will be able to afford one on Ebay
<cr1901_modern>
afford a DX7*
<ZirconiumX>
Great, but if I have a DeLorean you'll have both a DX7 *and* extra time
* cr1901_modern
segfaults
<cr1901_modern>
Anyways, good rant, thanks for all participants for allowing me to do so and give me feedback :). I genuinely feel a bit better this morning!
* cr1901_modern
better attempt some actual work today
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<cr1901_modern>
whitequark: CD theory of operation is on topic, btw lmao. I put it in the topic after it became my pet interest for about a month last year. l_oliviera is the person to ask about CD controllers... whenever he's around.
<whitequark>
ehhh
<whitequark>
i mean it'd be kinda fun to do glasgow run memory-cd
<whitequark>
but it'd require a player that lets me tap the bitstream, so something really old
<whitequark>
same problem as the modern floppies
<cr1901_modern>
True, and I was more interested in how the laser assembly work (and how it relates to the interface provided by old cd controllers) rather than reading CDs at the time.
<cr1901_modern>
CD controller documentation preservation is also pretty bad.
<cr1901_modern>
Well, old* controller docs
<cr1901_modern>
It's multiple chips divided by purpose- fair enough. But often you'll be lucky if you find 2 of the 3 or so datasheets required to put them all together
<whitequark>
hm
<whitequark>
the one TC showcased had docs for all three chips
<whitequark>
and it's freaking old, older than me
<whitequark>
in fact i could make an applet for it very easily
<whitequark>
except i have nfc where to get a player this old
<cr1901_modern>
How old? 80's?
<whitequark>
'89 iirc
<cr1901_modern>
My commentary is on Sega CD, where ppl are actually interested in simulating the latency of getting CD data into RAM to get certain games to work propely (and 1-4x CD-ROM bandwidth is... shitty lmao).
<cr1901_modern>
I'll have to take a look at the vid
<whitequark>
... you can store MIDI in CD subcode?
<cr1901_modern>
That's news to me if you can. Idk much about actual CD layout. Need to fix that.
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<cr1901_modern>
whitequark: Did your video discuss how the "52x" and above CD ROM read speed is an utter lie once you start reading the outer parts of the groove :)? The RPM becomes too great to maintain that level of speed, so a modern CD ROM falls back
<whitequark>
nope
<cr1901_modern>
well, that's one of your cursed fun facts for the day then :)
<l_oliveira>
information on directly controlling CD drive chipsets are like wizardry or black magic
<l_oliveira>
lol
<l_oliveira>
people who have it usually don't talk about it due to lack of interest or NDAs
<cr1901_modern>
Well, the CD chipsets I'm interested in are divided by purpose- one for controlling the lasers, another for error correcting and unscrambling into Redbook, and then yet another which sends data out using something an actual MCU can use
<l_oliveira>
I got some talk about CD stuff here before, I am not a specialist but I have some experience on repairing them, I kind of have a good view of the blocks that form a CD drive and we went on talking based on that experience
<cr1901_modern>
But that's also probably a bit wrong too, b/c aren't ppl looking for MCU program code for the Sega CD?
<whitequark>
i'd be pretty happy if someone just made a board with all the analog parts
<andlabs>
can we have an open hardware CD drive controller please
<andlabs>
that would be really nice
<andlabs>
it's been 40 years
<andlabs>
drop the nonsense
<l_oliveira>
well, there are several "levels" on that. Talking to the SEGA-CD MCU is a very high level at that
<whitequark>
wait really? there's actual interest in this?
<cr1901_modern>
you'd be surprised
<l_oliveira>
the MCU talks to the DSP and lens control on a completely different protocol than the host system is aware of
<whitequark>
hm
<l_oliveira>
there are some datasheets from SONY which contain information on DSP registers
<whitequark>
so if someone made a board with TDA8808 and TDA8809...
<whitequark>
i'd probably get nerdsniped into making some part of the digital control circuit
<whitequark>
think you can still get those easily
<l_oliveira>
There is some sort of industry standard command set for the CD MCU
<l_oliveira>
which is why the SEGA-CD BIOS can get away controlling SONY, JVC and Funai CD drives on the SEGA-CD
<cr1901_modern>
whitequark: Sure, and at some point a vendor decided to add an MCU into the mix for actually getting data off a CD-ROM. Idk how it fits into the whole scheme of "laser control -> error correction -> Redbook -> something the host processor can actually use"
<cr1901_modern>
or whether my phases/pipeline are even accurate
<cr1901_modern>
(It's not the host's responsbility to decode Redbook)
<andlabs>
I'll be completely honest
<andlabs>
I wanted to do lowest-level-possible bit stream dumps of CDs
<andlabs>
but I take it that CDs are not a single linear stream
<andlabs>
or even a series of linear streams
<andlabs>
*parallel linear streams
<cr1901_modern>
it's a single groove?
<andlabs>
that would mean it's a single linear stream
<whitequark>
yep
<andlabs>
which is what I want to rip, in a low level and uncorrected way
<andlabs>
I was under the impression that CDs had multiple groove streams
<cr1901_modern>
you would need a laser for that
<andlabs>
if there's a microcontroller I can build myself that allowed me to read that without interpretation that would be the most ideal thing ever
<cr1901_modern>
I mean, not difficult to get one... but _making_ a laser :P?
<l_oliveira>
andlabs: there are the groove and two lasers used to control the tracking, perhaps that's what gave you that idea?
<whitequark>
andlabs: would be easy to hack an old enough drive to do this
<whitequark>
where you can cut the traces to tracking control
<andlabs>
probably
<andlabs>
@ l_oliveira
<l_oliveira>
they take the laser beam and split it in three with a special collimation lens
<andlabs>
whitequark: sure, I guess? depends on how old
<cr1901_modern>
yea, and this is where my knowledge ends :P
<l_oliveira>
the middle beam follows the groove and returns the data, the other two are used to make sure the middle one stays focused and centered
<andlabs>
I take it you can't do this with modern drives, even with software control on linux?
<andlabs>
or with a custom kernel code
<l_oliveira>
and the PS1 protection actually process the difference between the two edge beams with a comparator opamp
<cr1901_modern>
I very highly doubt it
<cr1901_modern>
^ andlabs
<l_oliveira>
the license letters are encoded there, on the difference of the tracking beams
<andlabs>
how do OS get the TOC then?
<cr1901_modern>
l_oliveira: ... that's simultaneously really beautiful and fucking gross
<l_oliveira>
the MCU needs the TOC more than the OS, right? lol
<andlabs>
also I have to get a ZoomFloppy for doing the same with C64 disks
<l_oliveira>
the host system can query the MCU for the TOC at any time after the disc has been analyzed by the drive
<andlabs>
those are just GCR-encoded floppies but there are Complications
<andlabs>
apparently the g64 file format was not good enough despite being a raw GCR dump
<cr1901_modern>
andlabs: if you're tapping the laser, you'll want an ADC to return you the raw pits and grooves. But you need to actually _find_ the groove. And that requires you to have some feedback system to do it reliably.
<cr1901_modern>
unless it's possible to manually move the laser into position w/ fingers and I doubt that
<l_oliveira>
the action of reading TOC by the drive is usually automatic, the host system does not need to do anything
<andlabs>
thjere's now a nib file format with a source-available thing called nibtools but there's a lot of wonk about that -- apparently the tools were drived from GPL code but the current have no license
<andlabs>
and also there is a SVN repo but no link to it on the main website
<andlabs>
not good
<l_oliveira>
a discman usually the CD MCU also controls the display and read the user keys
<andlabs>
cr1901_modern: yes, a motor mechanism would be necessary here
<andlabs>
I'm not going to build an entire laser =P
<andlabs>
but I don't see how this couldn't be done with off-the-shelf parts
<l_oliveira>
it can of course
<andlabs>
which reminds me, I bought a bunch of EEPROMs from tfw8b
<l_oliveira>
you could for example use a SONY mechanism, servo driver and DSP
<andlabs>
so I guess at some point I will be entering the wonderful world of hardware engineering?????????
<l_oliveira>
then code your own MCU to have full low level control over the drive hardware
<cr1901_modern>
>(11:09:22 AM) l_oliveira: it can of course
<cr1901_modern>
It can?
<andlabs>
also if I do that it would be totally cool if I could also build a tape drive or vinyl record player
<andlabs>
with ZERO wow and flutter
<andlabs>
for as-perfect-as-possible archival
<l_oliveira>
for example the PC Engine CD unit
<andlabs>
lol
<andlabs>
I forogt aboutt hat
<andlabs>
that one is silly
<l_oliveira>
is built with the vanilla SONY chipset from Discman D-50
<cr1901_modern>
See, here I'm thinking that it's possible to build discrete versions of the focus control units
<cr1901_modern>
they wouldn't be GOOD
<andlabs>
PCECD uses raw addresses for all data access
<cr1901_modern>
but they could work
<andlabs>
it's not even red book audio
<l_oliveira>
but it has a custom MCU from NEC instead of SONY's
<l_oliveira>
PC Engine CD is so old the discs aren't using ISO9660 format
<l_oliveira>
but the physical data encoding is yellowbook actually. that's why you can copy PC Engine games normally with CDRs
<l_oliveira>
just read them RAW and it will do fine
<andlabs>
wait, when was the PCECD again?
<andlabs>
Sega CD was late 1990 and it uses ISO9660
<l_oliveira>
1988
<l_oliveira>
1991 SEGA CD
<l_oliveira>
MEGA-CD, SEGA CD was 1992
<andlabs>
>same year as the PCE
<andlabs>
space is warped and time is bendable
<l_oliveira>
PCE is 1987 actually lol
<cr1901_modern>
l_oliveira: Before I forget my q completely... if I had access to the correct parts of the laser assembly, how "outside the realm of reality" would it be to make a feedback system for the laser focus from discrete op amps (high quality)?
<l_oliveira>
CD came surprisingly fast for it, only one year after release
<whitequark>
cr1901_modern: it shouldn't be that hard
<andlabs>
[11:15:19] <l_oliveira>PCE is 1987 actually lol
<andlabs>
my comment still stands
<cr1901_modern>
I'm just not sure how to interleave the info from the positional feedback into a full control system
<l_oliveira>
1987 = white PCE with only hucards
<cr1901_modern>
positions aren't independent
<l_oliveira>
1988 = IFU-30 + CD ROM drive + System card 1.0
<andlabs>
if I was alive at my current age in 1987 I would have released my own 68000 computer designed specifically to prevent antipiracy mechanisms and I would have developed a super low cost 16-bit 44100hz DAC that would strongarm CD drive manufacturers to make a low-level CD drive
<andlabs>
it would have also used a flat framebuffer with Porter Duff compositions and alphablending
<l_oliveira>
Even the PC FX have no protection mechanisms
<l_oliveira>
first systems with protection were the PS1 and Saturn
<l_oliveira>
the Saturn protection are actually much, much more impressive than the SONY one which was more of a clever trick
<andlabs>
not unless you coult the NES and SNES's combined antipiracy/antiunlicensed
<andlabs>
and maybe to a lesser extent TI's silly GROM
<l_oliveira>
the PS1 got breached so fast it wasn't even funny
<l_oliveira>
didn't GROM actually rely on the TMS9918 videochip?
<l_oliveira>
sorry for deviating, I find TI stuff fascinating (heh)
<andlabs>
though I can't imagine anyone would be interested in pirating the over 80000 educational programs and over 30000 slightly different finance programs for the TI 99/4A
<andlabs>
seriously after looking at a library of TI 99/4A releases it's no wonder no one wanted the NIB TI 99/4A I got a fewe weeks ago for ... $20
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<andlabs>
probably the last retro computing deal that will ever be that good =P
<l_oliveira>
TI99 is such a bizarre computer
<andlabs>
the Editor/Assembler cart is fascinating
<andlabs>
a text editor
<andlabs>
a ***NOTEPAD***
<l_oliveira>
having to use the video chip as work ram makes me think about how slow it can be at doing things
<l_oliveira>
that has a image which may help you understand the big picture
<l_oliveira>
DVD and BD still work on the same principle
<cr1901_modern>
Cool, thanks for all your help :)
<l_oliveira>
you're welcome
<cr1901_modern>
As if this isn't clear by now, but my knowledge of optics kinda bites
<l_oliveira>
you certainly know aa lot more than me
<l_oliveira>
I just have a lot of general knowledge due to what I do for work
<cr1901_modern>
Idk how lasers work lol. I'm still stuck in that "everything is a ray" phase from high school lmao
<l_oliveira>
lol
<cr1901_modern>
pretty sure that doesn't apply to lasers and focusing
<cr1901_modern>
>so common mode change (data pits) doesn't affect tracking
<cr1901_modern>
I guess the idea is that on more modern CD controllers, "just let the DSP remove the common mode stuff" is what ppl do instead of using a diff amp
<l_oliveira>
what a PC sees on a ATAPI CDROM drive is completely different from what the drive is doing internally
<l_oliveira>
the protocol and virtualization makes it seem like a "fancy harddrive" from the point of view of the programmer
<l_oliveira>
but at low level it's nothing like that
<l_oliveira>
it works more like a tape deck
<cr1901_modern>
Of course. I'm just still trying to figure out where the CDROM DSP fits into all this, since TIL it's _possible_ (if not a good idea) to successfully track a groove using the assortment of analog building blocks.
<l_oliveira>
if you hit play and not collect the data it is playing the thing goes playing and the data keeps overflowing at the data buffer
<cr1901_modern>
better than underflow during a burn :P
<l_oliveira>
but the protocol controller hides that completely from the PC by pausing the drive when a sector is collected and not read
<cr1901_modern>
TLDR: CDs are cool. Just like floppies. But they're a mess :P.
<l_oliveira>
so it becomes as synchronous as magnetic media can be
<l_oliveira>
magnetic media have rings not grooves, so you have to kick the servo yourself to move tracks
<l_oliveira>
FUNNY ENOUGH
<cr1901_modern>
Well on floppies, we use stepper motors and hope for the best
<l_oliveira>
the Famicom Disk System works like a CD
<l_oliveira>
it has a groove not ringed tracks
* cr1901_modern
covers his ears blah blah blah
<cr1901_modern>
I don't want to- aaaaargh
<cr1901_modern>
I didn't want to hear that
<whitequark>
cr1901_modern: wait why do you need DSP for tracking at all
<l_oliveira>
it's so they can use DC motors instead of steppers lol
<l_oliveira>
HOW CHEAP YOU ARE NINTENDO
<l_oliveira>
so, FDS is like a tape laid on a disc
<cr1901_modern>
whitequark: I don't think you do. I'm still currently confused about the time era (late 80s? Early 90s?) where a dedicated DSP was added somewhere in the "laser to data" pipeline.
<cr1901_modern>
>(11:15:05 AM) l_oliveira: @cr1901, early 1982 CD Players were build like that and some even had gas based lasers
<l_oliveira>
very fast, you don't need to rewind it. the drawback is that you only get like 64KB of data per side
<whitequark>
cr1901_modern: can you show me the source for DSP being used for tracking?
<cr1901_modern>
And this comment made me think that early 80s CD drives had no DSP at all, but it became "convenient" for tracking by the late 80's.
<l_oliveira>
very early players use analog comparators for both focusing and tracking
<cr1901_modern>
No, I can't show you a source, because I don't think I understand myself where the DSP fits it :P
<cr1901_modern>
So I'm asking q's to clarify. Apologies for not making this clear
<l_oliveira>
later ones with powerful MCUs and DSPs can use them to cheap the lens control
<l_oliveira>
so it will be software based on later designs
<l_oliveira>
and then you have the problems of coils burning when the firmware crashes
<cr1901_modern>
byuu is looking for _either_ DSP code or MCU code for the Sega CD controller chip set
<l_oliveira>
(Yamaha CDR-100, early Pioneer DVDR writers, the PS2)
<cr1901_modern>
I don't remember which
<whitequark>
l_oliveira: ouch
<cr1901_modern>
But by the early 90's, at least one conversion to the digital domain is used to get from "laser to data"
<cr1901_modern>
errr, I said that wrong
<l_oliveira>
I can tell you drives from circa 1990 were still using analog feedbacks to control the lens
<cr1901_modern>
Good enough info for me :P
<l_oliveira>
look the datasheet for SONY CXA1081 and CXA1082 chips
<cr1901_modern>
Those are _very_ similar to the Sega CD chipset IIRc
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<l_oliveira>
these are the chipset used on the early discman designs
<cr1901_modern>
although not identical
<l_oliveira>
these ARE the chips used on the SEGA-CD2
<l_oliveira>
and on the PC Engine CD
<cr1901_modern>
ahhh, interesting
<cr1901_modern>
one of those datasheets I could find
<cr1901_modern>
the other I have no idea if it's online
<l_oliveira>
CXA1081 is the laser/photodiodes control
<l_oliveira>
CXA1082 is the lens/motors actuator control
<l_oliveira>
they're a married pair lol
<cr1901_modern>
And IIRC for Sega CD there are two other chips... one for EFM decoding to Redbook
<l_oliveira>
Sanyo
<cr1901_modern>
and the other that demuxes Redbook from CDROM
<cr1901_modern>
since it's not the Sega CD's responsibility to decode redbook
<l_oliveira>
LC8901 or something like that
<cr1901_modern>
Something like that?
<l_oliveira>
that takes the I2S audio stream and turns into data blocks
<cr1901_modern>
Does the Sanyo chip combine the EFM to Redbook and Redbook demux into a single chip?
<l_oliveira>
the DSP is a SONY CXD1167 I think
<l_oliveira>
DSP deals with EFM
<cr1901_modern>
Ahhh
<l_oliveira>
outputs I2S PCM
<l_oliveira>
I2S PCM is noise when the disc track is CD-ROM, which the Sanyo chip then decodes into CD ROM data
<cr1901_modern>
whitequark: I think to answer your q re: a Glasgow decoder, you probably want to Glasgow to take the EFM output and then decode that and decide what you want to do with it
<l_oliveira>
EFM is used the same way on redbook discs or yellow book, the thing is like when they added NTSC on top of the M TV system to make sure old sets would still be able to watch NTSC-M video as they would before
<l_oliveira>
so the red book part is still there as usual, the new stuff (sanyo chip) is used to deal with yellow book stuff when present
<l_oliveira>
electrical schematic for the CD block
<cr1901_modern>
I'm... surprised this is publicly available
<l_oliveira>
the MCU is NEC uPD75P008GB
<cr1901_modern>
Almost certainly a "VLIW DSP", correct :P?
<l_oliveira>
I dunno if it existed back then because that DSP is a 1980s chip
<l_oliveira>
that is a revision of another DSP which used external RAM chips
<cr1901_modern>
(To be perfectly clear, when I've been saying "MCU" and "DSP" for the past hour, I've been making a distinction.)
<cr1901_modern>
(As if modern CD ROM controllers require both an MCU and DSP)
<l_oliveira>
the previous version required a pair of 6116 SRAM chips to function hence why it has so many pins tied to GND (unused pins)
<cr1901_modern>
(If I'm wrong about that, now's the time to clear it up :P)
<l_oliveira>
on early designs the DSP only dealt with CIRC (Reed Solomon?) and EFM decoding
<l_oliveira>
the MCU deals with things like which track is being played, which second is being played, the host wants to change the track, is the lid closed, etc
<l_oliveira>
like a modem
<l_oliveira>
a modem has a data pump DSP which only deals with the transmission
<cr1901_modern>
> the MCU deals with things like which track is being played, which second is being played, the host wants to change the track, is the lid closed, etc
<cr1901_modern>
On Sega CD, I believe is the 68k's responsibility?
<l_oliveira>
and a more common CPU which deal with the hayes protocol and flow control/what the host wants
<cr1901_modern>
Ahh
<l_oliveira>
on US robotics modems the "normal" CPU usually was a I80186 SoC
<l_oliveira>
like the Sportster 28800
<l_oliveira>
I still happen to own one lol
<cr1901_modern>
Modems are another level of hell
<l_oliveira>
I never realized that modems are similar to CD players in that aspect until I needed to give you this example
<l_oliveira>
lol
<cr1901_modern>
It might be fair to say that "laser to data" on CD-ROM is a solved problem whose theory of operation is badly documented in 2019?
<cr1901_modern>
unless you know where to look already and what chips to put together
<cr1901_modern>
(and even then, it's more involved than floppy disk theory of operation)
<l_oliveira>
that's a good way of putting it
<l_oliveira>
because the problem doesn't exist practically. It just works and nobody thinks about it
<l_oliveira>
only people who deal with the hardware at very low levels (repair/development and now emulation) need to know the details
<cr1901_modern>
it will likely become a problem as CDROMs start to decay without their info having been preserved otherwise.
<cr1901_modern>
See e.g. Domesday project
<cr1901_modern>
And even CDDA... plenty of stuff whose source has been lost
<cr1901_modern>
(seeing a master compact disc press copies is... something)
<cr1901_modern>
https://www.youtube.com/watch?v=LEnmSem8C-0 Okay my spoons are gone for now lol, thanks for the help and the convo from everyone involved. Very productive :D.
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<andlabs>
I HOPE a ZoomFloppy and nibtools will be sufficient for C64...
<l_oliveira>
I am sure what is being learned on Domesday project can be easily applied to CDs and DVDs later on
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<balrog>
cr1901_modern: have you been following #domesday86 ?
<balrog>
one planned/WIP feature is combining multiple rotted dumps
<balrog>
;)
<balrog>
(also #domesday86 is their project IRC channel)
<balrog>
also there's work under way to extend this to tape
<balrog>
VHS is messy though, since you need to capture two analog streams simultaneously for hifi-stereo
<cr1901_modern>
also it is a helical drum
<cr1901_modern>
which sucks
<cr1901_modern>
err, well the signal is stored helically*
<balrog>
you'd still be using the VCR's head and relying on its tracking
<balrog>
(which means if the control track is messed up, you might have to do more work)
<balrog>
the "fun" part is that VHS is common enough that data recovery companies have already done all this R&D, proprietary and behind closed doors
<cr1901_modern>
oh, see when I last looked into this in... 2010? the consensus was "we'd never been able to create a VHS read/write head from hobbyist means". Not sure this is still true, but I do consider the helix format to be pretty awful.
<balrog>
yeah — the idea would be to leverage an existing read head from a VCR
<cr1901_modern>
I've added #domesday86 to my channels, but I'll have to stagger it in and out as needed; ETOOMANY
<balrog>
like we leverage existing hardware for the laser / read amp / tracking for laserdisc with the domesday duplicator
<cr1901_modern>
And ditto w/ CDs I presume?
<cr1901_modern>
I love the no-bullshit power supply on the linked blog
<balrog>
yeah (though for now I think they're reading CDs in a tapped LD player)
<balrog>
(because later LD players would play audio CDs)
<cr1901_modern>
Oh right, LD and CD use the same laser
<cr1901_modern>
Anyways, the magic q... how much is it to get one of these. I already know it's beyond my budget right now, but this is good to know
<balrog>
do you have an LD player / would you want one // or would you want to hook this up to a CDROM drive?
<cr1901_modern>
The latter is more in line with my interests. LD player at this point for me as "nice to have, not essential".
<cr1901_modern>
I have no less than 5 sacrificial CD rom drivers
<cr1901_modern>
drives* even
<balrog>
$79+shipping for a DE0-nano board, $49+shipping for an FX3 board. I'm not sure how much the dd boards were, iirc someone recently did a run but they were blank boards
<balrog>
before buying I'd suggest discussing it because the analog filters might have to be different for cdrom